Multiple outlet system for audio frequencies



June.25, 1940. c. R. WALLACE ET AL 2,205,447

MULTIPLE OUTLET SYSTEM FOR AUDIO FREQUENCIES Filed Aug. 23. 1938INVENTORS C.R.WALLACE R.BURGE.$S

ATTORNEY.

MULTIPLE OUTLET SYSTEM FOR AUDI FREQUENCIES Clarence E. Wallace andRichard Burgess, United States Marine Corps Application August 23, 1938,Serial No. 226,276

8 Claims. (01. 179-1) (Granted under the act of March 3, 1883, asamended April so, 1928; 370 o. G. 757) Patented June 25, 194% Thisinvention relates to a multiple outlet audio system, especially adaptedfor instruction and practice in receiving code signals.

Among the several objects of this invention are:

To provide means of distributing energy at audio frequencies, to any oneor more of several outlets, from a single source of supply, without theload on any outlet affectingthe quantity of energy supplied to any otheroutlets connected to the same power source;

To eliminate cross talk and other energy to idle outlets from the loadson active outlets;

To provide means for controlling any one, or all, of several outletsfrom a switch at any one of the outlets;

To provide means for controlling the energy supplied each outlet withoutvarying the output of the energy source.

The single figure of the drawing shows schematically one embodiment ofour present invention.

It is frequently desirable to distribute energy to each of a number ofoutlets connected to a common source so that the response at each outletis identical, for example, in giving instruction or practice in thereception of code signals by radio. It is essential for the successfuloperation of such a system that it be possible to connect any number ofthe outlets to the common source without afiecting the volume of outputat any outlet that may be already connected and in use, without thenecessity of varying the output of the source each time load is added orremoved by connecting or disconnecting additional outlets. Theserequirements are successfully met by our invention.

A source of audio-frequency energy, such as an audio-frequencyoscillator may be connected to the terminals I to supply energy to theseveral transformer primaries 2 connected in series in the outputcircuit of the source. It is to be understood. that any desired numberof primaries may be used up to the capacity of the source available.Coupled to each primary 2 is a secondary 3, constituting with theprimary a transformer of the air core type having very low elliciency oftransformation for audio frequencies and so wound that the impedances ofthe outlets are matched by the respective transformers. As an example,in devices embodying our invention heretofore made and used each primaryhas 1350 turns and each secondary has 1500 turns, but these values aregiven by way of illustration and not of limitation. By usingtransformers having the characteristics mentioned there is no change inthe output of one due to drawing load from others or ceasing to drawload from others. In fact, it is possible to connect twenty suchtransformers in our apparatus and short-circuit the secondaries ofnineteen of these without causing appreciable change in the output levelof the iremaming secondary. Hence, once the output of the source issatisfactorily adjusted, it need not be varied thereafter to compensatefor changes in the number of outlets being used.-

- Associated with each secondary coil 3 is a sound translating device 4such as a head phone, provided with a variable resistance 5 shuntedacross it to permit individual adjustment of signal strength in thetranslating device 4. minal of each translating device 4 is connected bya lead 5 to a grounded conductor 6 that is also connected by a lead I toone terminal of transformer secondary 3 and is connected to a fixedrelay contact 8, the other terminal of the translating devicev 4 beingconnected to a lead 9 to a fixed relay contact l0 and also connected tothe movable relay contact II. The other terminal of secondary 3isconnected to a movable relay contact I2. A coil source l4 upon closingthe key l5 actuates the One terl3 energizable from movable contacts Hand I2 to move contact I l from its normal closed circuit position toopen position away from contact 8 and to move contact [2 from its normalopen circuit position to closed a l and has both terminals groundedthrough lead.-

6 and also that transformer secondary 3 has one terminal grounded. Thiscompletely prevents cross talk or other transfer of energy from anactive outlet, to an idle one. This is very advantageous in that thetransformers may be located at some distance from the devices 4 and allwires connecting the devices 4 to their respective secondaries may bebunched, that is, not transposed or individually shielded. Closing keyl5 energizes relay coil [3 and breaks the circuit between contacts 8 andH while simultaneously closing the circuit between contacts Ill and I2,thereby disconnecting the device 4 from the ground connection and makingan operative circuit between the device 4 and its respective secondary.Jacks I6 are connected to each relay coil l3 to permit combining, byinter-connecting or patch cords, more than one relay coil in a circuitcontrolled by any key l5 associated with a coil so connected. Thispermits one person, for example, an instructor, to control the supply ofsignals to the various devices 4 so connected.

The invention herein described and claimed may be used and/ormanufactured by or for the Government of the United States of Americafor governmental purposes without the payment of prising an audio energysupply circuit including a plurality of air core transformer primariesin series, a secondary inefficiently coupled to each primary, a fixedrelay contact connected to one one side to said fixed contact, a secondfixed contact disposed to coact with said movable con: tact connected tothe other side of said device,

a second movable relay contact disposed to.co-'

act with the first said fixed contact and connected to said second fixedcontact, said second movable contact being normally in circuit closingrelation with the coacting fixed contact to ground said device and saidone side of said secondary, a relay coil disposed to break the circuitat said second movable contact and close the circuit through saidsecondary and said device at said first movable contact when energized,means including a switch to energize each said relay coil, jack meansconnected to each relay'coil to permit selectively connecting said'relaycoils together in a desired combination controlling more than one relaycoil by one said switch, and an adjustable resistance across each saiddevice.

2. A multiple outlet audio energy system, comprising an audio energysupply circuit including a plurality of air core transformer primariesin series, asecondary ineflibientlycoupled to each primary, a fixedrelay contact connected to one terminal of each said secondary and amovable relay contact connected to the other terminal thereof, means toground each said fixed contact, a sound translating device connectedatone side to said fixed contact, a second fixed contact disposed tocoact with said movable contact connected to the other sideof saiddevice, a second movable relay contact, disposed to coact with the firstsaid fixed contact and connected'to said second fixed contact, saidsecond movable contact being normally in circuit closing e19,-

1 tion with the coacting fixed contact to ground said device and saidone side of said secondary, a relay coil disposed to break the circuitat said second movable contact and close the circuit through saidsecondary andsaid device at said first movable contact when energized,means including a switch to energizev eachsaid relay coil, and anadjustable resistance across each said device. l 1 l 3. A multipleoutlet audio energy system, comprising an audio energy supply circuitincluding a plurality of air core transformer primaries in series, asecondary inefiiciently couply to each primary, a fixed relay contactconnected to one terminal of each said secondary and a movable relaycontact connected to the other terminal thereof, means to ground eachsaid fixed contact, a sound translating device connected at one side tosaid fixed contact, a second fixed contact disposed to coact with saidmovable contact connected to the other side of said device, a secondmovable relay contact disposed to coact with the first said fixedcontact and connected to said second fixed contact,said second movablecontact being normally in circuit closing relation with the coactingfixed contact to ground said device and said one side of said secondary,a relay coil disposed to break the circuitat said second movable contactand close the circuit through said secondary and said device at saidfirst movable contact when energized and means including a switch toenergize each said relay coil.

4. A multiple outlet audio energy system, comprising an audio energysupply circuit including a plurality of air core transformer primariesin series, a secondary inefiiciently coupled to each primary, meansgrounding one terminal of each said secondary, a sound translatingdevice, an adjustable resistance connected across said device, meansnormally connecting said device to ground but actuatable to connect saiddevice across said secondary instead of to ground, operating means toactuate each of said connecting means to connect the respective deviceto the corresponding secondary and means selectively connectible torender more than one of said operating means subject to a singlecontrol.

5. A multiple outlet audio energy system, comprising an audio energysupply circuit including a plurality of low efficiency air coretransformer primaries in series, a secondary coupled to each saidprimary, a sound translating device associated with each said secondary,a variable resistance across each said device, means operable to connecteach said device and one terminal of the coacting secondary to ground orto connect said device across the respective secondary, and meansselectively connectible to render more than one of said connecting meanssubject to a single control.

6. A multiple outlet audio energy system, comprising an audio energysupply circuit including a pliuality of air core transformer primariesin'series, a secondary coupled to each said primary, a sound translatingdevice associated with each said secondary, a variable resistance acrosseach said device, means operable to connect each said device and oneterminal of the coacting secondary to ground or to connect said deviceacross the respective secondary, and means selectively connectible torender more than one of said connecting means subject to a singlecontrol.

7. A multiple outlet audio energy system, comprising an audio energysupply circuit including a plurality of air core transformer primariesin series, a secondary coupled to each said primary, a sound translatingdevice associated with each said secondary, means operable to connecteach said device and one terminal of the coacting secondary to ground orto connect said device across the respective secondary, and means viceacross the respective secondary, the parameters of said transformersbeing so evaluated that operation of any number of said devices does notdiminish the energy supplied to any other said device.

CLARENCE R. WALLACE. RICHARD BURGESS.

